Dead starting battery, fully charged house batteries? Is this possible?

[TechTonics]

I left my headlights on for a few hours last night, and noticed before I went to bed

Shut them off around 1030, and went out this morning and the starting battery is dead. I have solar panels that charge the 2 house batteries and the display shows 13.9 (full or close to it).

Is that possible? I thought if the house batteries are charged that the starting battery would also be charged?

And yes, I know about the little button under the hood that cuts-off the starting battery if the house batteries draw too low. It’s pressed-in

Am I wrong? Is this just a simple “left the headlights on” situation? Or is it possibly a bigger deal?

[TechTonics]

Also, when giving an attempt, it rolls over (weakly) and then the (half possessed) Viper alarm system goes off

[boywonder]

It depends on what battery isolator/separator that you have...some are unidirectional (alternator to starting and house batteries, solar only charges house batteries) and some are bi-directional (solar charges both batteries).


The Blue Sea ACRs are bi-directional, Surepower separators are avail either way depending on model #.....not too familiar with other models.


..so we need more detail on your isolator/separator.....

[TechTonics]

The van is a 2001 and I believe the SMB conversion was done in 2003

Apologize for my noob status, but I can’t figure out how to upload a pic from my phone.

Txt me? and I’d love to send you some pics!

[Scalf77]

SMB conversion done in 2003 would have a diode based isolator. (This also goes along with the little push button reference, they usually had a resettable circuit breaker installed with a little push button). It would not be bidirectional, meaning that the solar charger will not charge the start batteries.

-greg

[boywonder]

here is a picture of techtonic's isolator..





I would recommend one of the Blue Sea ACR's....if you are on a budget there's the 7610 (I have this one..works great) or a fancier one that handles more current and has more features..the 7622


The Surepower 1315 separator is bi-directional as well; it's old school relay coil...the Blue Sea ACR's are solid state devices.

[Scalf77]

That is the circuit breaker, the isolator will look more like this:



In any case, it would not be bidirectional. My general recommendation would be to use a Blue Sea 7622 or 7622. When you also install the switch you a get a full range of choices from On, Auto and Off, LED status, and failure blink codes if needed. While not completely "solid state" the relay they use is a latching relay, so there is no power used while it is on or off, only when changing state.

The 7610, 7611 are both FET based, and would get the job done, don't give you some of the same features. Be careful to size the wires correctly, as they usually recommend upsizing due to temperature.

With the BlueSea 7622 installed, you could have pretty much jumped the starter from the house system and been on your way.

-greg

[boywonder]

I was thinking that was the smallest isolator yet! Should have asked if he had the usual blue anodized unit...

Originally Posted by Scalf77

My general recommendation would be to use a Blue Sea 7622 or 7622.

-greg

Obviously...Greg is quite fond of the 7622

[TechTonics]

Right! I’ll get a pic of my isolator later.

Either way, it sounds like just a low battery, and the full-charge on the house batteries won’t mean the starting battery is full...right?

Hypothetically, if I got stranded and this happened when I was on a solo trip, could I jump the starter battery off the house batteries? (Given long-enough cables?)

[loper]

On my home made van project I wired in two circuit breakers just to be able to jump start the van from the "house" batteries.

I needed a circuit breaker going into the Redarc charger/isolator anyway, so I added another one that will bypass the charger and connect both battery banks.

I can take the charger out of the loop this way, so I don't accidently fry it. Once the motor starts I can return the breakers to the "normal" configuration and business as usual.