Big Battery Maintainer
 

I'm looking for a maintainer for 2 batteries that are connected together.

I have a small camper with a starting battery, and a deep discharge (house) battery (to run things). They are connected via a Yandina which is a solid state switching device.

The battery tender jr. and other 2 maintainers I have aren't able to charge both batteries.

I'm thinking I could a big powerful maintainer that could be plugged into one battery and keep it charged enough that the Yandina would open the gates to allow charging current to flow to the other (house) battery.

Any ideas?

Once one is fully charged it should switch to charging the other .
A house charger that autoswitches to maintain should work if your “house” Battery is flat .
I have a @$30 one from Home Depot . You could “buy and try” for 30 days ?

Here’s the instructions in case you don’t have them

https://www.emarineinc.com/pdf/Yandina%20Combiner%20Combiner%20100%20Instruction% 20Manual.pdf

Here’s the one i bought .
Think it was homedepot and think it was around $30. But it was a few years ago

https://www.amazon.com/Schumacher-XCS15-SpeedCharge-Battery-Charger/dp/B004EIDCFO

Is it 24V or 12V?

I have one of these guys in my RV. Does a fine job on 6 volt batteries wired in series.

https://www.progressivedyn.com/rv/charge-wizard/

If you have 12 volts wired in parallel make sure they are the same age - otherwise it will overcharge one - if the other gets weak.

it's a 12 V circuit

Aren't you just talking about a 12v smart charger with a "float charge" mode?

On my bass boat, I just used Battery Tenders on all three Optimas (one starting, two trolling with a 12/24 switch on the foot control)...those two could be charged via a single plug up front....never did.

Look into that mebbe...

https://www.amazon.com/Schumacher-SC-600A-CA-SpeedCharge-Frequency-Battery/dp/B000H94F6E

I have a few of these. Never hurts a battery to leave connected, but they were about $30 when I bought them.

Honestly, as long as you are simply maintaining the battery, just about anything should do the float work for you. It does not take much to keep the batteries full.

For charging, I would size the charger for normal recharge at battery size in amp-hours divided by 20.

So, 200 AH of storage, charge at 10 Amps. Also a 3 stage or 4 stage charger is the best, which reduces the current as you approach 14.4V on a re-charge.

Thanks - I see a 3 stage one that appears to be something Stanley, B&D etc. slap their labels on...

https://www.walmart.com/ip/STANLEY-15-Amp-Battery-Charger-with-40-Amp-Engine-Start-BC15BS/38243759


I'm not sure why the smaller units aren't working, but capacity seems to be the only idea I can come up with.

The Yandina may be the problem? Say it's designed to begin charging the 2nd battery when the primary one is charged to 13 volts? Well, if the primary battery is old, won't charge to 13V anymore, what then?

yes, it might be the Yandina design - I sent it back to them, they tested it, and swore it was just fine

both batteries are new (these problems eventually ran down the old ones)

also, they both charge using the alternator (on the hwy)

Have a multimeter? Maybe check battery voltage at the posts when you believe both batteries charged by the alternator. Not all new batteries test great, depending on how long they were in the system before they were sold.

A little $pendy at around $70, but I recently bought a harbor freight battery tester that measures milliamps between the posts. Has good reviews on youtube...more accurate than a load tester. https://www.youtube.com/watch?v=kNyiigm7x14

I dunno...maybe replace the yandina with some sort of manual 3 way switch, carry a multimeter to test voltage?

Anyway, sounds as if your current maintainers aren't putting out enough for your yandina to open up and charge both. Your alternator if working well should be putting out around 14 volts.

That should work fine.

Thanks again!

I do (including a 5 digit one and a data-logger that reads nV) but they read fine when charged by the alternator.

I do know other people are using the Yandina on the same type (manf./model) of vehicle, and it works fine - I suspect they are driving the things more often. FWIW, it is a Vanagon - a cult vehicle (and I see guys putting enormous labor & $$ into these things, when could do that to a nice 911 instead... go figure)

12V chargers don't do well with multiple batteries. Probably they way they calculate the float voltage, might be an average or something. I converter my RV to 12 volt parallel batteries when my 6 volt series one exploded on the side of hte highway (long day). However one battery started failing before the other. ...the 12V charger tried to "keep up" and destroyed the second by overcharging it.

The only time there is a problem is when they are "out of sync" with each other. Or if they have different capacities. Or the cables connecting them have different resistance. Or if they are different ages.

I design large battery banks using 200AH, 12V batteries, up to 48VDC and up to 96kWh (40 batteries). You need a good equalizing system and to have it run weekly. Anything much bigger, these days, and you are better off with the extremely large single cell units (1000-2600 AH, 2V cells), strung in series.

A couple of 12V-200AH batteries, if they are the same age, charge and the charging connection is equal, shouldn't be a problem.