multiple charging source problem

[REO]

I recently installed Ll house batteries. I also installed a Balmar DC to DC charger to charge my starting battery from the house batteries. A 20 amp charger is still in place from the original system for charging at the dock. I also installed an 80 amp inverter charger for dockside charging the house batteries. I am considering connecting the 20 amp charger to the starting battery. With this configuration my starting battery will receive a charge from the DC to DC charger and the 20 amp charger at the same time.
I asked a Balmar tech support person if this is an acceptable configuration. He said that it could overcharge the starting battery. That doesn't seem right.
The DC to DC charger is limited to 30 amps and the ac 20 amp charger will be connected to both the starter and generator batteries, reducing the charge at the starter battery to about 10 amps. Is charging from two sources a problem? What happens if I also install some solar charging at the house bank?

 

[SteveK]

What loads are on the start battery when on the dock that deplete the start battery which requires a constant charge from multiple sources?

My start batteries are fully charged when I shut down engines and with no load can hold enough charge for weeks, maybe months and are ready to start the engines.

 

[Bmarler]

It seems like the old charger could be kept for an emergency charging source. Seems overkill to have it on when the dc to dc is keeping the start battery topped up. If the dc to dc goes bad, the old charger can top up the start battery using the inverter. ( or dock power)
One problem with multiple charge sources is that there can be different charge profiles. Absorb and float settings can fight each other if the chargers aren’t fully programmable. I am assuming though, that the existing charger is not fully programmable. If it is, you should be able to match charge profiles.
Adding solar shouldn’t be a huge problem, as long as you can set the charge profile to compliment the inverter charge. Most solar chargers are fully programmable, plus, solar is really doing its work when not on dock power.

 

[REO]

Hadn't thought about the different charge profiles. The old charger is not programmable. I am able to turn it off at the ac circuit breaker panel, so I guess it becomes a back up charger.

 

[REO]

Good point about the need to charge the start battery at the dock. Likely I will never need the extra charger.

 

[Bacchus]

I'm no Li expert but my impression is that most folks installing a DC-DC charger are doing so to provide charge TO the house bank FROM the start bank. The reason as I understand it is so the alternator charging the start bank operates normally and the DC-DC charges the house w/o risk to the alternator.
Normally the start bank is only slightly depleted at start and returns to full charge quickly from the Alt.
At the dock it seems like the higher A charger programmed for LI makes sense and the lo A charger only serving start makes sense.
Do you have a thruster? I had both B&S thrusters run off my house bank which didn't make sense to me. I switched the thruster to my start bank to leave a pure house bank as only time thrusters would be running is w/ eng running & alt providing boost to the thruster/ srart bank

 

[REO]

I do have a thruster run off the start bank. I have a Balmar unit to protect the alternator. Maybe it makes sense to charge the start bank first, in some instances but my external regulator will allow the 125 amp alternator to deliver a bigger charge than the start bank could absorb and the DC to DC is only capable of 30 amps. So, charging the house bank first maximizes the house charge rate.

 

[Bmarler]

the thruster off the start bank is a bit of a conundrum, i still think i'd aim the alternator at the house bank though. if the thruster duty cycle is pretty high maybe consider increasing the size of the start bank.
definitely something to consider. or make a way to easily turn on the backup charger to the start bank, running off the inverter, to help the start bank during thruster use.

 

[SteveK]

@REO
If you have a single engine with that large ALT, and have the proper configuration for LFP batteries, I agree the ALT should charge the house bank directly, then a DC2DC or a auto combiner to top up the start battery.

I also agree with thrusters and winches to run off the start battery while engine is running as they are better designed for that purpose (high amp short term).

I have twins and an engine start and a genny start. Each start battery has a dedicated ALT which can also be combined. Then I use DC2DC from each to the house bank. My Alt's are not configured for LFP.

 

[REO]

I have not yet used the new set up. However my engine starts almost instantly and I rarely use the thruster. The question will be how much will the windlass draw down the start battery if it is used for a long hard pull. The engine will always be running, but it may not keep up with the draw. I am using 2 -100 amp batteries in parallel for engine/etc. battery.

 

[Iggy]

I am no expert ether. What I can tell you is that I too are using LI for my house bank. I am using 2 30A dc to dc chargers from the starting bank when underway. Also a 3000W charger/inverter to charge them when on shore power. With a 100A charge output.

For the starting bank I am using I am using a 17A charger. To keep it topped off. All chargers are set to the correct settings. AGM or Li with the correct voltage settings too.

The settings are very important. Oh, the external reg from the Alt (120A) is set to AGM for the starting bank. Now my setup is just the opposite of yours but still using more than one charger. After 2 seasons, no problem have come up.

My understanding is, as long you are using 3 or 4 stage chargers that they will shut down when the batteries are fully charged automatically.

 

[Iggy]

I have not yet used the new set up. However my engine starts almost instantly and I rarely use the thruster. The question will be how much will the windlass draw down the start battery if it is used for a long hard pull. The engine will always be running, but it may not keep up with the draw. I am using 2 -100 amp batteries in parallel for engine/etc. battery.

This is another reason why the Alt charging my starting bank first. Plus no protection device is needed for the Alt.

With all the work that Alt is doing. I installed a heat sensor to prevent overheating.

 

[REO]

The issue that convinced me to run the alternator output to the house bank is charge rate. We spend lots of time at anchor, and expect to draw the house batteries down a lot more than the starter/windlass batteries. The 120 amp alternator with Balmar external regulator will deliver a high charge rate to the big house batteries. The Balmar DC/DC charger is limited to 30 amps. Hopefully, that will be enough to keep the engine battery charged. I did install a heat sensor from the regulator to house batteries. I don't think the DC?DC charger accepts a heat sensor. That was one of the tech reps concerns about using two dissimilar charging sources.
After considering input, I'm going to connect the 20 amp charger to my generator battery. That battery is only charged by its small alternator. I'm looking forward to getting the boat back in the water and trying out the new system. Lots of things to monitor.

 

[twistedtree]

Maybe it makes sense to charge the start bank first, in some instances but my external regulator will allow the 125 amp alternator to deliver a bigger charge than the start bank could absorb and the DC to DC is only capable of 30 amps. So, charging the house bank first maximizes the house charge rate.

A high output alternator like you have is exactly the situation where, and the reason why it's preferable to have the alternator directly charge the LFP house bank. Having the alternator charge the house bank, then using a DC/DC charger to charge the LFP bank only makes sense if you have alternator output capacity that is less than or equal to the DC/DC capacity. Otherwise you are not fully utilizing your alternator capacity, and losing one of the big advantages of LFP.

 

[Iggy]

All all can say is, there is more than one way to this.

For me I have 60A from the Dc to DC chargers when the engine is running to the house bank. Not great but not bad, giving that the Alt is not ways putting 120A. Keep in mind that the Alt also needs to supply current to other house loads when running.

On the other hand, I can start my genset and use the charger/inverter to recharge the house bank when on the hook at 100A. As far as the DC to DC chargers over heating. Victron has a heat sensor built in. So it will back down if needed. I did install some sheet metal behind the DC to DC chargers to act as a heat sink. Not the best heat sink, but better than nothing.

The other reason I went this way and most likely it will not happen is. The the BMS shuts down I can transfer the load to the starting batteries by using two switches. One disconnecting the house bank and the other transferring the load to the starting batteries.

 

[REO]

Iggy
You are correct. There are many ways to skin this cat....whatever that means.
I think I resolved my original issue. I'm convinced that it is not a good idea to charge a battery with multiple chargers if they do not use the same charging profile. I solved that issue by moving the 20 amp charger to the generator battery. On the other hand (and there is always another hand) if I need a bit more charge to the engine batteries I will get a charger that can have an exact matched charging profile to the DC/DC charger. I think you have determined that that will work.

 

[SteveK]

@Reo, I have not read that your ALT and regulator were reconfigured to charge Li. Also, a battery temp sensor is not recommended for Li.

My setup has a 60 & 40 amp DC2DC for relay charging the house Li at 100A while underway from start. I did this as my ALT does not have configure for Li, the DC2DC do. No Bat temp sensor. I chose this route rather than new ALT's.

 

[REO]

I converted my alternator from internal to external regulation so I could configure for LI. I have installed the 2 temp sensors from the Balmar external regulator to the LI battery and alternator. The regulator is configured for LI. I spoke to a tech at Balmar today and he said that he "kind of" agrees that a battery temp sensor may not be needed on LI batteries. However, the regulator requires both sensors to provide over temp protection for the alternator. If I do not use the battery sensor, the alternator overheat system does not work. He said that the reason some people do not use the battery temp sensor is that it reduces the voltage by .1 volt when the battery becomes warm. However it will also shut down a hot battery before the BMS. This .1 volt reduction is new info for me. I have a good battery monitoring system, so I will be intrested in how this works in real life.

 

[SteveK]

so you have one temp sensor on Li and one attached to the ALT?

Can you post the regulator model #. I am now curious to read up on how it functions. By the sound of it, this is an add on regulator to ALT that did not have one before. It seems as though it is programmable to Li profile.

 

[Iggy]

Iggy
You are correct. There are many ways to skin this cat....whatever that means.
I think I resolved my original issue. I'm convinced that it is not a good idea to charge a battery with multiple chargers if they do not use the same charging profile. I solved that issue by moving the 20 amp charger to the generator battery. On the other hand (and there is always another hand) if I need a bit more charge to the engine batteries I will get a charger that can have an exact matched charging profile to the DC/DC charger. I think you have determined that that will work.

With that understanding, you should be fine. Just to be clear, I installed a temp senor on the Alt, not the Li battery bank since one is not needed.

I am no pro, but after 2 seasons I am happy with the results and with no problems.

I don't think 0.1 volt will change anything as far as usage is concern.

 

[REO]

SteveK
The external regulator I used is Balmar MC 618-H
To install it you must remove the internal regulator from the alternator and install a conversion module. It is a little unit that fits over the brushes. It is progamable for Li. It can have the optional temp units installed.

 

[Bmarler]

SteveK
The external regulator I used is Balmar MC 618-H
To install it you must remove the internal regulator from the alternator and install a conversion module. It is a little unit that fits over the brushes. It is progamable for Li. It can have the optional temp units installed.

that's the regulator i'm using. it's really versatile, especially if you install the smart shunt and bluetooth adapter as well. the bluetooth app lets you program and monitor from your phone. really nice for fine tuning the system. you can make adjustments on the fly without having to be at the regulator with the little magnet probe. virtually every parameter is accessible, i believe the temp related voltage reduction is user adjustable as well, so you can tailor it to your specific battery manufacturers specifications.

 

[SteveK]

SteveK
The external regulator I used is Balmar MC 618-H
To install it you must remove the internal regulator from the alternator and install a conversion module. It is a little unit that fits over the brushes. It is progamable for Li. It can have the optional temp units installed.

Thanks. I found the install manual, but I cannot find if my alternator can be made to work. It is a single wire positive to battery, no name branded. While it has three terminals at bottom, no idea what they are for. Anyone know.

 

[Bmarler]

Thanks. I found the install manual, but I cannot find if my alternator can be made to work. It is a single wire positive to battery, no name branded. While it has three terminals at bottom, no idea what they are for. Anyone know.
View attachment 146022

most internal regulated alternators can be converted by bringing out the field wire. that's a pretty small looking alternator though, if it's got a low amp output it might not be worth it.

 

[REO]

I got the replacement module from the alternator supplier. Mine is a 120 amp internally regulated that is commonly converted. Yours may not be that easy.

 

[SteveK]

Agreed. I had already dismissed the idea until this thread made it seem worth considering. I get about 75A out of each ALT so they supply 100A thru DC2DC to house, and that has worked so far.
Wait till I tell the admiral I dont need to do this job.

 

[Bacchus]

Iggy
You are correct. There are many ways to skin this cat....whatever that means.
I think I resolved my original issue. I'm convinced that it is not a good idea to charge a battery with multiple chargers if they do not use the same charging profile. I solved that issue by moving the 20 amp charger to the generator battery. On the other hand (and there is always another hand) if I need a bit more charge to the engine batteries I will get a charger that can have an exact matched charging profile to the DC/DC charger. I think you have determined that that will work.

When I did some mods on my charging system I completely separated my gen batty and relied on the gen alt to charge the batty. My multi bank shore charger then was charging similar size (8D I know not the best and will replace them when needed) and chemistry (all AGM). I implemented a suggestion from a TF member replacing the gen on/off switch w a 1-2-all-off switch (same foot print & mounting) with a jumper to my house. This allows emergency back up to start gen as well as a way to periodically top off the gen batty.
You might consider doing something similar to allow isolation of the gen as well as ability to manually cross connect gen batty (and small charger) to your start bank if needed in a pinch or to top off start bank if needed. This would be a manual energy back only.

 

[Iggy]

When I did some mods on my charging system I completely separated my gen batty and relied on the gen alt to charge the batty. My multi bank shore charger then was charging similar size (8D I know not the best and will replace them when needed) and chemistry (all AGM). I implemented a suggestion from a TF member replacing the gen on/off switch w a 1-2-all-off switch (same foot print & mounting) with a jumper to my house. This allows emergency back up to start gen as well as a way to periodically top off the gen batty.
You might consider doing something similar to allow isolation of the gen as well as ability to manually cross connect gen batty (and small charger) to your start bank if needed in a pinch or to top off start bank if needed. This would be a manual energy back only.

That is a good idea! I wish I thought of that because when I bought my boat there was no genset battery switch. So of course, I installed one. I could have went a step farther...

What I did do and mainly for the winter months when the boat is on the hard. I installed a ARC (automatic charging rely) with a switchable breaker. So when visit the boat and plug in. The starting battery charger will top off the genset battery too. I switch it off, during boating season.

But I have been thinking of removing the genset battery and using the starting batteries for both. Right now I have 4 banks of batteries, house, genset, starting and thruster. It would be nice to remove one of them. If needed, I can use the house bank to start too. But still on the fence for doing just that. If I was in a real bind, I do have the bow thruster bank. But that means moving batteries.

If anyone has any toughts on this, please share them.

 

[Portage_Bay]

When thinking about what to do if I run main engine starting bank flat and the house bank not up to starting the mains because it's too low, admittedly not likely, then the gen is the last resort. Fire up the gen, charge the batts up and get going again. For that reason I want the gen independent from other banks. The gen start batt is a group 27 tucked in close to the gen not taking up much space.

That is a good idea! I wish I thought of that because when I bought my boat there was no genset battery switch. So of course, I installed one. I could have went a step farther...

What I did do and mainly for the winter months when the boat is on the hard. I installed a ARC (automatic charging rely) with a switchable breaker. So when visit the boat and plug in. The starting battery charger will top off the genset battery too. I switch it off, during boating season.

But I have been thinking of removing the genset battery and using the starting batteries for both. Right now I have 4 banks of batteries, house, genset, starting and thruster. It would be nice to remove one of them. If needed, I can use the house bank to start too. But still on the fence for doing just that. If I was in a real bind, I do have the bow thruster bank. But that means moving batteries.

If anyone has any toughts on this, please share them.

 

[Bmarler]

That is a good idea! I wish I thought of that because when I bought my boat there was no genset battery switch. So of course, I installed one. I could have went a step farther...

What I did do and mainly for the winter months when the boat is on the hard. I installed a ARC (automatic charging rely) with a switchable breaker. So when visit the boat and plug in. The starting battery charger will top off the genset battery too. I switch it off, during boating season.

But I have been thinking of removing the genset battery and using the starting batteries for both. Right now I have 4 banks of batteries, house, genset, starting and thruster. It would be nice to remove one of them. If needed, I can use the house bank to start too. But still on the fence for doing just that. If I was in a real bind, I do have the bow thruster bank. But that means moving batteries.

If anyone has any toughts on this, please share them.

i removed my genset battery as it was chronically getting over charged. i hardly use the genset anyway. i already had cables and switches installed to start it from the start bank, so just enabled it there. i can always add it back if i think i need it in the future. my start bank is huge anyway, as is my house bank. i have solar charging the house bank, (and start bank too with an acr) and can parallel the house/start from the helm at a push of the button. the genset battery was just not needed at this time.
my method may not work for some if their start bank is modestly sized. in that case a dedicated genset battery can make sense. a person needs to have a good understanding of their individual needs.