RO Water for Batteries?

[Sidclark]

Six new Trojan 105's come in this week and the thought occurred to me. Can I use RO water from my watermaker to top off the batts?

 

[KnotYet]

Always use distilled because I would be worried that the RO might be malfunctioning.
Also, I have occasionally had a bit of growth in the RO storage tank that needed cleaning.
If you are somewhere so remote you can't get distilled and the batteries are getting
low then RO water will be better than tap water.

 

[bshillam]

Dehumidifier

I would say if you run a dehumidifier on the boat that's better! I typically on a wet day can get a quart to two.

 

[firehoser75]

I agree with KY! Carry a gallon of distilled water. It is not that hard to store, and a gallon should last all season (or more).

 

[jleonard]

I agree with KY! Carry a gallon of distilled water. It is not that hard to store, and a gallon should last all season (or more).

I typically go thru more like 2 + gallons per season with 4 GC batteries.

 

[caltexflanc]

This will be handy for you. If you have further questions, call Trojan, they are usually very helpful.

https://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf

 

[dhays]

FWIW, when I was using wet cells, I just used the water off the dehumidifier that we always had running on the boat when we were away from it. I ran the hose from the dehumidifier into a water bottle set in the galley sink. I it would fill up and overflow into the sink. It meant that I always had a convenient amount of distilled water available for the batteries.


The water from the dehumidifer is actually distilled, not RO. I used it for years with no problems.

 

[firehoser75]

Jay,
I have 6 golf cart house batteries, and use about 1 gallon per cruising season or about 1.5 gallons per year. At $1.49 per gallon, not a big expense!!
I only run a dehumidifier in the winter, so it is definitely better and easier to just use the bottled gallon containers of distilled water for $1.49 each

 

[KnotYet]

FWIW, when I was using wet cells, I just used the water off the dehumidifier that we always had running on the boat when we were away from it. I ran the hose from the dehumidifier into a water bottle set in the galley sink. I it would fill up and overflow into the sink. It meant that I always had a convenient amount of distilled water available for the batteries.


The water from the dehumidifer is actually distilled, not RO. I used it for years with no problems.

Dehumidifier water contains whatever ions are suspended in the boat environment air.
There is no 'brine' component as there is with RO water. You know that residue that
ends up on surfaces inside your boat before you turn on the dehumidifier? It winds up
in the discharge tank. Then in some cases it winds up in the battery electrolyte.
Kidding aside, there's no comparison to distilled water. Dehumidifier water has no filter
to remove dirt and organics that are routinely airborne along with the moisture.
That being said, flooded batteries contain gallons of electrolyte and some impurities can
be tolerated for sure.

 

[tiltrider1]

I’ve used tap water for years and typically get 8-10 years out of my batteries. I think lack of water is a bigger issue than tap water. Now, I’m not saying tap water is as good as distilled, I’m saying Type of water is less critical than some people make it out to be.

 

[KnotYet]

I’ve used tap water for years and typically get 8-10 years out of my batteries. I think lack of water is a bigger issue than tap water. Now, I’m not saying tap water is as good as distilled, I’m saying Type of water is less critical than some people make it out to be.

In Seattle you should have been using rain water!

 

[DennisB1]

Seems like high boil off, What are your charge and float voltages during operation and when connected to shore power?

 

[Lepke]

I've been using RO water for more than 10 years. I use 8Dd & 8Dc batteries. Last ones lasted 9.5 years for deep cycle and about 8 for starting. Could have gone longer. Dyno batteries.

 

[FF]

"In Seattle you should have been using rain water!"

All rain water contains condensation nuclei and should be filtered or at least allowed to settle the dirt for a couple of days.

https://www.google.com/search?client=firefox-b-1-d&q=condensation+nuclei

 

[Brooksie]

RO water is de-mineralized and fine for storage batteries. Have been using it for decades.

However, some RO systems have re-mineralizers.

 

[bayview]

Condensate from a dehumidifier is full of undesirable stuff.

 

[Sidclark]

Seems like high boil off, What are your charge and float voltages during operation and when connected to shore power?

Our last boat had 440 AH battery bank consisting of four golf cart batteries from Costco. It seems they drank water like crazy. I checked and rechecked charging parameters to make sure that was ok. The charger was a ProNautic charger at 50 amps. Great charger. The only thing I could think of causing all the water usage was that we lived on the hook nine months out of the year depending on those batteries. Three months were in a marina. On the hook, 500 watts of solar took care of charging. I see folks on here using a gallon or so a season and I wish I could say the same. I was using gallons and gallons, to the point it was a nuisance keeping the batts topped up. I would have rather changed the oil then to top the batts.

The current boat has a 660 AH bank so maybe with a little more reserve I won't be drawing the batteries down so deep. With the 440AH they were taken down close to 50% on a regular basis.

 

[FF]

Hydrocap |

Batts that work hard always require more water than those that mostly sit on a charger.

These caps need to be purchased for your set up and room to install them .

 

[ksanders]

I’ve used RO water for years and got 9 years out of my last house bank.

 

[KnotYet]

Hydrocap |

Batts that work hard always require more water than those that mostly sit on a charger.

These caps need to be purchased for your set up and room to install them .

X2 for Hydrocaps. They seem to last at least as long as the batts and minimize the
need for constant watering.

 

[Sidclark]

Hydrocap |

Batts that work hard always require more water than those that mostly sit on a charger.

These caps need to be purchased for your set up and room to install them .

I just got a quote back from the Hydrocap folks. $235.10 with shipping..

 

[AKDoug]

When I flush my RO unit after making water, it cycles RO water through the membrane in the flush cycle. The sampling tap shows less than 25 ppm at the end of the flush, typically 165-250 when making water to fill the tanks. Depending on how your system works, I would use the RO flush to fill batteries.

Moot point for me, as I have AGM's

 

[FF]

"I was using gallons and gallons, to the point it was a nuisance keeping the batts topped up. I would have rather changed the oil then to top the batts."

"I just got a quote back from the Hydrocap folks. $235.10 with shipping"

Which do you value more , your time or some currency?

 

[EngNate]

Battery water should be free of all contaminants and minerals. You will keep adding water through the life of the batteries and the minerals will stay and become concentrated. 'Good' RO water may have up to 400ppm dissolved solids. Tap water can be far higher than that, or it can in some cases be quite low. The best RO water is around 100-150. Distilled water is zero, and deionized very close to that. I use the condensate from my dehumidifier, it is distilled water. One could catch the condensate from an A/C unit and save it - but be sure there's no debris or salt water getting into it. My T125's are in their 8th year of service on dehumidifier water.

 

[Boatcrazy]

following

 

[BruceK]

I usually bought "Demineralized" water at the supermarket. Good enough?

 

[O C Diver]

Distilled water from Walmart is less than a dollar a gallon. Usually less than 2 gallons a year. Seems pretty straightforward to me.

Ted

 

[dhays]

Distilled water from Walmart is less than a dollar a gallon. Usually less than 2 gallons a year. Seems pretty straightforward to me.

Ted

Yeah but Ted. That would mean actually going to Walmart. I'll do a lot to avoid that.

 

[DDW]

You can buy a resin based deionizer for less than $100. Make your own deionized water. When the media is new, the TDS will be zero or close to it. When you get up to 10 ppm the media is close to needing replacement.

Both distilled and deionized water has 'stuff' in it. Just different stuff. For a battery deionized water may be better.

 

[O C Diver]

Yeah but Ted. That would mean actually going to Walmart. I'll do a lot to avoid that.

I'm sure a premium priced grocery store will sell you the same gallon of water with their label on it for 50% more. If that makes your conscience whole, I completely understand.

Ted