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 switchhttp://www.harborfreight.com/750-watt-continuous1500-watt-peak-power-inverter-69660.html***3 HF 1000W w/"fixed" on/off switchhttp://www.harborfreight.com/1000-watt-continuous2000-watt-peak-power-inverter-60704-9815.html

I don't think the 750w inverter nor the 1000w one will do the job as described. eg, the PD converter has a power factor of 0.7 which makes its VA draw on the inverter near or over 1000.Meanwhile the alternator has to be able to run the inverter and the vehicle and there are limits to that. I tried a version of doing that charging method and posted about it some time ago. In my case I powered a 600w Vector 35a charger from a 1000w MSW inverter (no advantage to have PSW for this job) that worked ok, but the limit was in the truck.The inverter was connected to the truck's battery with short fat wires so that was ok. The truck engine running (in idle--revving made no difference with this truck) was able to keep the truck's voltage (dash meter) needle pointing up at 14v as long as the inverter load was not too much.When I tried to increase the inverter load by adding a second Vector charger but set to less than 35a at the 20a, I found the inverter could handle it (300w at 20a vs 600w at 35a so 900w total) but now the truck's voltage fell off, needle sagging down to the left. 10a more ok needle stays up quivering like it is on the verge of sagging down to the left again. So that is the limit. Got to keep the truck's voltage holding at 14v. (It helped when I shut off the truck's climate control too!)So the OP set-up could work given that:-the chosen inverter is high enough in watts to supply the VA draw of the PD converter, and-The vehicle's 12v supply will be 'strong' enough to run the inverter plus the vehicles own requirements to hold its voltage at 14v. I know you can do better connecting from the alternator instead of the battery, so the OP method could be better than what I did for that part.

BFL13 wrote:I don't think the 750w inverter nor the 1000w one will do the job as described. eg, the PD converter has a power factor of 0.7 which makes its VA draw on the inverter near or over 1000.1000VA ONLY at full load, 55A (maximum)charging rate to house battery = ~65A input current to the inverter. Additional loads on the PD should be minimal when underway.Meanwhile the alternator has to be able to run the inverter and the vehicle and there are limits to that. I tried a version of doing that charging method and posted about it some time ago. In my case I powered a 600w Vector 35a charger from a 1000w MSW inverter (no advantage to have PSW for this job) that worked ok, but the limit was in the truck.The inverter was connected to the truck's battery with short fat wires so that was ok. The truck engine running (in idle--revving made no difference with this truck)That seems not just improbable but practically impossible.As the engine revs rise the amperage production capability of the alternator will rise accordingly. Unless this particular alternator could produce maximum current output (90A?) at or near idle and that maximum current was somehow being "used" at the time. Both highly unlikely.Or was the chassis battery (and house?) fully, DEEPLY, discharged during your test? was able to keep the truck's voltage (dash meter) needle pointing up at 14v as long as the inverter load was not too much.But what was the total of other loads on the chassis alternator/VR system>When I tried to increase the inverter load by adding a second Vector charger but set to less than 35a at the 20a, I found the inverter could handle it (300w at 20a vs 600w at 35a so 900w total) but now the truck's voltage fell off, needle sagging down to the left. 10a more ok needle stays up quivering like it is on the verge of sagging down to the left again. So that is the limit. Got to keep the truck's voltage holding at 14v. (It helped when I shut off the truck's climate control too!)So the OP set-up could work given that:-the chosen inverter is high enough in watts to supply the VA draw of the PD converter, and-The vehicle's 12v supply will be 'strong' enough to run the inverter plus the vehicles own requirements to hold its voltage at 14v.Most MSW inverters do not shut down until the input voltage drops to <10.5volts I know you can do better connecting from the alternator instead of the battery, so the OP method could be better than what I did for that part.The factory wiring between the alternator and chassis battery will not be critical at the maximum charging rate to the battery.PS: What was (is?) your alternator output rating?

The MSW didn't matter with the Vector charger, but it would matter with the PD converter. That brand is known to need PSW where a WFCO does not ISTR.I don't know how the truck's 12v system all works. I gather they have some variations in what you can do among different trucks. I described what happened in my case. My alternator is 105amps.I figure the same sort of thing will happen with any version of that method, but the limiting factor amounts would be different. Same limiting factors though. Inverter limit and truck limit.Only way to find out what yours will do is try it. BTW it is no use running the inverter at just above its alarm off voltage for its input, when the truck won't run on that low a voltage. You have to keep the truck's voltage up to normal 14v. It (mine)doesn't sag down a little below 14 and stay there. Once it starts to sag it just keeps dropping like a collapse.

Hi,The cut off point for me is 12.9 volts. When that is displayed I reduce the load on the alternator.

BFL13 wrote:The MSW didn't matter with the Vector charger, but it would matter with the PD converter. That brand is known to need PSW where a WFCO does not ISTR.I don't know how the truck's 12v system all works. I gather they have some variations in what you can do among different trucks. I described what happened in my case. My alternator is 105amps.I figure the same sort of thing will happen with any version of that method, but the limiting factor amounts would be different. Same limiting factors though. Inverter limit and truck limit.Only way to find out what yours will do is try it. BTW it is no use running the inverter at just above its alarm off voltage for its input, when the truck won't run on that low a voltage. You have to keep the truck's voltage up to normal 14v. It (mine)doesn't sag down a little below 14 and stay there. Once it starts to sag it just keeps dropping like a collapse.Your truck SHOULD run on 12.0 volts for certain, and most probably as low as 10-11 volts, the latter possibly with ABS (and other) fault lights, but "run" she should.Remember that the goal is to reliably and safely charge the house battery while underway, no engine idling issue there.

IDEA...charging house battery(set) underway. | Good Sam Community

eb145
Explorer II
Jul 18, 2014
OP,

I think this is exactly what you are looking for:

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

Ed
Naio
Explorer II
Jul 17, 2014
Thank you, ken white and MEXICOWANDERER! I probably will start my own thread :).
MEXICOWANDERER
Explorer
Jul 16, 2014
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
Explorer
Jul 16, 2014
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
Explorer II
Jul 16, 2014
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
Explorer III
Jul 15, 2014
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
Explorer
Jul 15, 2014
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
Explorer II
Jul 14, 2014
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
Explorer
Jun 19, 2014
I'm confused.
wwest
Explorer
Jun 19, 2014
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.