IDEA...charging house battery(set) underway.

[wwest]

It seems that the chassis alternator/VR system will often not fully charge the house battery(set) due to voltage drop between the two, or overcharge, boil the electrolyte away, for a deeply discharged house battery(set), especially dual 6 volt deep cycle batteries where in deep discharge is expected/common use.

Remove the chassis charge connection to the house battery(set) and wire it to the armature of a SPDT relay(***1) AND the input to a ~750W MSW inverter(***2). Then wire shore power 120 VAC supply source to the N.C. contact of the relay, and the 750W MSW inverter output to the N.O. contact. The common relay contact is now wired to supply power to your progressive dynamics converter.

The PD will now PROPERLY charge the house battery(set) under all conditions.

***1 12 volt armature, ~20A 120 VAC rated contacts.

http://www.ebay.com/itm/Lot-5-CIT-Relays-40A-14VDC-20A-120VAC-12VDC-Coil-Circuit-Board-A51AE12VDC1-6-/291165015807?pt=LH_DefaultDomain_0&hash=item43cac98eff

Upgrade to a 1000W(***3) inverter then you can safely parallel in the 120 VAC fridge supply input and not worry about propane use underway (or at all, EVER!).

***2 HF 750W w/"Fixed" on/off switch

http://www.harborfreight.com/750-watt-continuous1500-watt-peak-power-inverter-69660.html

***3 HF 1000W w/"fixed" on/off switch

http://www.harborfreight.com/1000-watt-continuous2000-watt-peak-power-inverter-60704-9815.html

[eb145]

OP,

I think this is exactly what you are looking for:

CTEK D250S DUAL - MPPT and dc/dc battery combo charger


Ed

[Naio]

Thank you, ken white and MEXICOWANDERER! I probably will start my own thread :).

[MEXICOWANDERER]

Unless you marathon coast-to-coast in July a motor vehicle alternator voltage regulator will not overcharge the house batteries. Keeping the voltage drop extremely low between alternator and house batteries however IS NOT SIMPLE OR EASY to fix and this is the area you should be concentrating on.

[ken_white]

Naio wrote:
Bumping, because I am still wondering what to buy :).

Will a good isolator, e.g. Sure Power also regulate the voltage to my house batteries, and change it according to their SOC? Or do I need to do something more?

An isolator does not regulate battery voltage, but rather will isolate the main and house batteries during discharge.

The vehicle alternator is regulated and it provides adequate charging for the main battery while the engine is running.

If the house battery is stored some distance away, and they are not getting charged while driving, the culprit is probably undersized charge cables.

The convertor will charge the batteries while connected to shore power.

EDIT: You should start a new thread that provides the background information for the questions you have and you will get lots of good advice from skilled members here.

[Naio]

Bumping, because I am still wondering what to buy :).

Will a good isolator, e.g. Sure Power also regulate the voltage to my house batteries, and change it according to their SOC? Or do I need to do something more?

[wa8yxm]

wwest wrote:
It seems that the chassis alternator/VR system will often not fully charge the house battery(set) due to voltage drop between the two, or overcharge, boil the electrolyte away,

Bad theory.. First: Your tow vehicle alternator, unless upgraded (Assumes a trailer) is not goign to love a really big load all that much, So the voltage drop in the wires,, Protects it.

On a motor home the alternator is likely bigger, but same applies.

Second: AS the battery charges, current flow drops. the closer the house battery gets to charged the less, and less and less current flows (Same for the starting battery by the way) and as the current approaches zero,, VOLTAGE drop approaches zero as well.

And then you went on to say "Or overchages" Clearly, if there is all that much voltage drop that's not going to happen.

Now: Why do the batteries dry out?

Well. With new batteries I need to water annually. as they age more often.. but... What converter do you have.. Some of them are well known for boiling batteries,, Some,, not so much.

[ken_white]

wwest wrote:
It seems that the chassis alternator/VR system will often not fully charge the house battery(set) due to voltage drop between the two, or overcharge, boil the electrolyte away, for a deeply discharged house battery(set), especially dual 6 volt deep cycle batteries where in deep discharge is expected/common use.

Remove the chassis charge connection to the house battery(set) and wire it to the armature of a SPDT relay(***1) AND the input to a ~750W MSW inverter(***2). Then wire shore power 120 VAC supply source to the N.C. contact of the relay, and the 750W MSW inverter output to the N.O. contact. The common relay contact is now wired to supply power to your progressive dynamics converter.

The PD will now PROPERLY charge the house battery(set) under all conditions.

***1 12 volt armature, ~20A 120 VAC rated contacts.

http://www.ebay.com/itm/Lot-5-CIT-Relays-40A-14VDC-20A-120VAC-12VDC-Coil-Circuit-Board-A51AE12VDC1-6-/291165015807?pt=LH_DefaultDomain_0&hash=item43cac98eff

Upgrade to a 1000W(***3) inverter then you can safely parallel in the 120 VAC fridge supply input and not worry about propane use underway (or at all, EVER!).

***2 HF 750W w/"Fixed" on/off switch

http://www.harborfreight.com/750-watt-continuous1500-watt-peak-power-inverter-69660.html

***3 HF 1000W w/"fixed" on/off switch

http://www.harborfreight.com/1000-watt-continuous2000-watt-peak-power-inverter-60704-9815.html

A big problem with this hypothesis is that the system losses have increased substantially due to the increased losses created by the additional power conversion processes and cabling/connections.

So if the charging system was inadequate before, it is now even more undersized...

There are other issues too, but no need to address those since the concept doesn't work.

[Naio]

Hello folks 🙂

I am trying to understand posts in this thread from people much more knowledgeable than I. I am also building a system from scratch (a conversion project). I know a moderate amount about electricity and batteries, but very little about cars and trucks.

Hence my questions, which may be pretty ignorant 🙂

- Is the voltage regulator a stock part of my truck? Not something added to RVs?

- If it is so 'dumb', can I improve the situation? Will a good isolator, e.g. Sure Power also regulate the voltage to my house batteries, and change it according to their SOC? Or do I need to do something more?

I have learned a lot from this thread already -- thank you all!

--
ETA: I see from this post http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27646735/gotomsg/27649731.cfm#27649731
that the voltage regulator is stock and may be inside the alternator. Google says mine is... and that the voltage output is supposed to be 16-17v. That does not sound good for my AGM house batteries, eh?

[mena661]

I'm confused.

[wwest]

BFL13 wrote:

wwest wrote:

BFL13 wrote:
The OP is mis-informed about the batteries boiling out when at low SOC and accepting lots of amps. I ignored that part of the OP to concentrate on the inverter/converter match etc.

Maybe the OP could post a diagram of his intended set-up so we could help with the details to get it so it would work. Especially since some people here already have done something like that.

"OP's house battery set is two 6 volt deep cycle (golf cart) batteries in series. Encountered almost complete boil off twice, both times ~300 mile drive immediately after only running on batteries for a weekend.

Alternator will source unlimited(***) AMPS as long as the battery set internal resistance is low, deep discharge.

*** In my case 90 amps in cruise mode.

Alternator output = 14.9 volts, house battery = 10.5 volts

4.4 volts X 90 amps = 396 WATTS, 200 watts/battery.

A lot of HEAT.

Not understood. I regularly charge at 14.8v and with two 6s at 50% to get them back to 90% I have used 70 amps charging where it stays at 70 amps for about half an hour to get the batts to 65% SOC, then amps taper for an hour and a half to get to 90%. Total time is two hours. Nothing "boils over"

If your house battery is at 10.5v it is totally dead and could be recharged from that (but not often or they will be toast!) so the time at constant amps of the charger would be longer. No boiling over. Why would it do that?

I have seen with batts that are really , really low, that at first they won't take many amps at all but after a while they start taking more. Kind of a reverse taper going higher. After a while the amps peak and you are back to normal and the amps then taper back down as normal.

Perhaps something exceptional happened there, which needs to be addressed, but don't take it as being normal. You normally recharge at 12.1v or about 50% SOC. What is all this 10.5v?????? Holy cow!

This discussion is about the functioning of an automotive battery charging system.

[wwest]

smkettner wrote:

BFL13 wrote:
Jeez PT, let the OP answer first. He may have been hitting the batts when so low that they can only accept 3 amps, with 90 amps, and no way to refuse. "Boiling over" might be the result.

I have hit plenty of batteries down below 10 volts with a shop charger on high max (15 volts?). The battery resistance is so high when dead they only accept a few amps and do not boil (gas). They just sits there. As the sulfate ions get back into solution the amps start to climb.

Shop owner said I should do the slow charge to avoid damage and turn the knob down. I replied worst case I will sell a battery as it is already shot. In the mean time I don't have all day to babysit this stuff and crank it back up.

Yes, I have brought quite a number of lawn tractor type batteries back to life with patience, 2-3 days on a charger. Very few "chargers" will force enough current flow to cause a serious level of outgassing.

Vehicular alternator/VR systems on the other hand....

[landyacht318]

Ok I have nothing but antagonistic replies which I will keep to myself, after the following.

Best of luck with whatever you are trying to sell.

[wwest]

landyacht318 wrote:
I've never slowly taken a battery to 10.5v, and I like BFL's hypothesis.

I wonder what the electrolyte level was before the 300 mile drive to the place where the batteries were takes to 10.5v. Was it the same set of batteries which twice had been"boiled nearly dry?"

Same batteries, still fully functional today. The first time it happened I only noticed because the time to charge depletion from 90% SOC was to short.

Any other heat sources nearby the battery?

No.

Don't more modern vehicles have some battery temp sensor on the chassis battery tray and adjust voltage accordingly? Perhaps this sensor is reading low.

Yes, many "smart" chargers use a temperature sensor in order to most rapidlycharge a battery absent overheating it. Our chassis VR's (discussion subject) are more DUMB than smart.

I've done many 4 hour drives returning from Baja with extremely depleted batteries without noticeable water loss, but they were wally world batts which almost never needed water, and I did not have an additional parallel alternator circuit to ekk out every last amp the alternator can muster, as I do now.

Perhaps you had a diode isolator, 0.5 volt drop minimum, or a less than robust isolator/house battery connection. In both of those cases the VR will only sense the chassis battery SOC.

[time2roll]

BFL13 wrote:
Jeez PT, let the OP answer first. He may have been hitting the batts when so low that they can only accept 3 amps, with 90 amps, and no way to refuse. "Boiling over" might be the result.

I have hit plenty of batteries down below 10 volts with a shop charger on high max (15 volts?). The battery resistance is so high when dead they only accept a few amps and do not boil (gas). They just sits there. As the sulfate ions get back into solution the amps start to climb.

Shop owner said I should do the slow charge to avoid damage and turn the knob down. I replied worst case I will sell a battery as it is already shot. In the mean time I don't have all day to babysit this stuff and crank it back up.