95 smb battery question

dckiteboards · 05-12-2020, 08:00 AM

We recently acquired a 95 smb , it's got the a.c./dc fridge , propane heater , a/c , etc. I have a friend who is changing his batteries on his sailboat and is pulling out two NPG 12-200ah 12 volt gel batteries and they are testing at 90 percent capacity, sorry for the noob question but can I run them? They are free

moorefc · 05-12-2020, 09:37 PM

If you can fit them and understand the care and feeding of gel (agm?) batteries go for it! The price is right as is the voltage... Lots of info on the latter here, search is your friend. AGMs do not like to stay discharged, etc...
Aux AC will consume a battery pronto...
Have fun

SMB123 · 05-12-2020, 10:06 PM

What house batt in there right now? If the same size, you can probably run them in parallel or just a single. I'd take 'em to Autozone for a test . What brought you to 90%? How old are they? I wouldn't hesitate to let 'em run their course if they have life. If you don't need to keep the fridge cold for more than a day you can even run 1. The fridge won't run very long even with two batts anyway, I reckon - may be wrong.

Solar is next :-)

dckiteboards · 05-13-2020, 02:25 AM

My buddy is a mechanic at the marina where this boat is kept and he has all sorts of equipment to test batteries and rehab them . So he is then one that installed the new batteries and ran tests on the old . Electrical is my weakness. This is my third round of batteries from him , every year they pull dozens of batteries out of boats ranging in size from 15feet to 100feet, the owners all want there yachts running tip top and so in with the new out with the old, all I pay is the core charge to take the old batteries . We have a 2015 transit with a build and I am running two agms in there with solar ,etc. Sportsmobile is a new one in our fleet . The smb had some 15 year old batteries in it when we got it .

Scalf77 · 05-13-2020, 05:43 AM

The charge settings of GEL batteries is usually different than flooded, or AGM batteries. The absorption settings are much lower, so you would want to make sure that your existing charger has the ability to match the charging parameters of a GEL battery, They also have a lower charge rate than a AGM, so again you would want to make sure your charge rate was not to high.

-greg

moorefc · 05-13-2020, 08:21 AM

As Scalf77 said, if in fact you have a gel battery, they require a different charge profile than other types, typically 14.0v - 14.2 (constant voltage charge) and float 13.1-13.3 and are known to be sensitive ie. life limiting to overcharging due to gassing....Your alternator is typically a bit higher (14.3-14.5) in terms of output and long drives...are they really gel?
Here is a nice summary table comparing characteristics of lead acid batteries
https://batteryuniversity.com/learn/...ased_batteries

Does your built in charger have charge profile settings? (my Fresno build did not) You have a starter battery in parallel typically that wants a higher charge/voltage that will be supplied by the alternator, so that is a consideration....
You could get sophisticated and go from alternator to inverter to a charger with a gel profile.....There is a nice write up on that here.

But, as you indicated, the price is right...