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pianotuna

Regina, SK, Canada

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Posted: 09/18/20 11:13am Link  |  Quote  |  Print  |  Notify Moderator

msmith1199 wrote:

BFL13 wrote:

She wants to keep the charging to 50 amps each so 100a for the two. Meanwhile there have been posts that the alternator will fry from trying to charge the thirsty Li house batts.

Sounds like the way to go is disconnect/disable alternator charging and just leave in the Aux start from the house feature if ever needed.


So is it likely that in most motorhomes there is no DC to DC charger and the alternator is just wired directly to the house batteries and charges them with whatever output it has?


Hi msith1199,

The alternator is controlled by the ECM of the chassis. Most alternators have a duty cycle rating. In my case, that is 120 amps. But continuous duty is 1/3 of that, or about 40 amps.

The only time one is likely to see greater amperage is if both the starter battery and the house batteries are "hungry" or if a large load is present in the house. For example the water heater on the electric setting.

I deliberately added a 2nd charging path from the Chassis battery to the house bank. I do have manual control of the connection. I have seen 70 amps for brief periods of time. I monitor the voltage on the chassis battery. If it gets to 12.3, I turn off the connection.

I've seen no complaints of burned out alternators. Maybe BFL13 could give us a link?


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, soon to have SiO2 batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

3 tons

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Posted: 09/18/20 11:14am Link  |  Quote  |  Print  |  Notify Moderator

pnichols wrote:

3 tons,

I'm wondering about your last sentence above.

Doesn't your 9245 automatically drop back to a 13.XX volt float voltage at some point when it's charging batteries?

I believe that LiFePo4 batteries have a recommended float voltage such that they can be left hooked up full time to a converter/charger that eventually settles at their float voltage, just like any other type of battery.

For instance Battle Born LiFePo4 batteries can be floated at 13.6 volts or lower indefinitely according to their specifications, so you shouldn't have to disconnect them from your 9245 when it drops down to it's float voltage.

As for when driving with the engine alternator hooked up to the batteries, after just a few minutes when things are warmed up, our RV's alternator settles in around to the mid-13's in voltage, anyway.


True with the 9245!....(except for the 21hr/15 min equalization cycle)...This is why I prefer the standard charger (with charge wizard in boost mode) to PD’s LiFePo4 offering, but once the battery has charged (and subsequently finished it’s BMS dance whereby current and voltage values briefly alternate..), I simply disconnect the battery (via basic knob switch atop battery post)...I mostly dry camp, so rely on solar and battery...

BFL13

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Posted: 09/18/20 12:04pm Link  |  Quote  |  Print  |  Notify Moderator

Don't have a link, but just an "ISTR" on alternator charging where the issue was, when you added fatter wire etc so you got more charging amps, and ran the fridge etc, that this would be more amps for longer than the alternator could take and it would heat up and die.

It might be bogus for all I know for sure. There is something about the alternators in police cars being able to take more than the ones in regular cars. I ASSume the ones in MHs are regular types. Although in a Class C, which is made from an "incomplete truck" that could have been made into an ambulance instead, maybe it would have the stronger type of alternator.

Here we have a worry that the Li batts might be harmed (can't say--seems situational?) and that the alternator might be harmed from too many amps (Li being low R etc, and the fridge on) so somebody who knows about all this should step in and clear it all up.


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msmith1199

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Posted: 09/18/20 06:10pm Link  |  Quote  |  Print  |  Notify Moderator

I won’t be leaving the motorhome plugged in all the time. It will only being getting 110 volts when we’re using it and plugged into shore power or when using the generator. We got the smaller motorhome specifically because we rarely stay in any one spot for more than a few days. So most of the use we’ll only be plugged in two or three days at a time. I do have power in my storage unit, but it’s only 15 amp 110v so I go down the day before I’m going to pick up the motorhome and plug it into that to turn the fridge on.


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steveh27

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Posted: 09/19/20 04:23am Link  |  Quote  |  Print  |  Notify Moderator

Here's a site I found:

https://shop.pkys.com/Alternator-Lithium-Battery.html

BFL13

Victoria, BC

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Posted: 09/19/20 08:14am Link  |  Quote  |  Print  |  Notify Moderator

https://shop.pkys.com/Alternator-Lithium-Battery.html

pianotuna

Regina, SK, Canada

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Posted: 09/19/20 10:08am Link  |  Quote  |  Print  |  Notify Moderator

Hi Steve,

But the existing alternator is not going to "see" the LI bank. And the existing alternator is controlled by the Chassis ECM.

In the E-450 the OEM house bank charging circuit is fused at 60 amps (for my unit). The 60 amp are hard to find--so I replaced mine with an auto reset circuit breaker rated at 50 amps. I did add a 2nd charging path with a 2nd circuit breaker, direct to the chassis battery. The wire in both circuits is #8.

Back in the old days when I was using double conversion for limiting shore power, the twin 30 amp fuses on the PD (30 amp) converter did "deform" (i.e. quasi melted). They did not, however, fail.

When I tried double conversion on a GFCI circuit that the Magnum would instantly trip, the surge current was such that the reverse polarity fuses went *poof* more or less instantaneously, due to inrush current from the Magnum.

So, I suspect, that an OEM charging system with replacement LI batteries would blow the fuse before the alternator would fail.

grizzzman

salt lake city, Utah

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Posted: 09/19/20 04:01pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

Hi Steve,

But the existing alternator is not going to "see" the LI bank. And the existing alternator is controlled by the Chassis ECM.

In the E-450 the OEM house bank charging circuit is fused at 60 amps (for my unit). The 60 amp are hard to find--so I replaced mine with an auto reset circuit breaker rated at 50 amps. I did add a 2nd charging path with a 2nd circuit breaker, direct to the chassis battery. The wire in both circuits is #8.

Back in the old days when I was using double conversion for limiting shore power, the twin 30 amp fuses on the PD (30 amp) converter did "deform" (i.e. quasi melted). They did not, however, fail.

When I tried double conversion on a GFCI circuit that the Magnum would instantly trip, the surge current was such that the reverse polarity fuses went *poof* more or less instantaneously, due to inrush current from the Magnum.

So, I suspect, that an OEM charging system with replacement LI batteries would blow the fuse before the alternator would fail.

My 2013 F150 output 14.0 at all times. My 2019 F150 output 12.7 to 12.9 over a period of 2 hours. Using a Renolgy 40 amp DC to DC charger is a buck/boost device and bumped the voltage to my preset 14.2 at the cost of less amps(34) If your looking for a solution this is what I would advise you look into.


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pianotuna

Regina, SK, Canada

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Posted: 09/19/20 06:08pm Link  |  Quote  |  Print  |  Notify Moderator

I guess it depends now the ecu is adjusted? Are they adjustable?

steveh27

Grosse Pointe Woods, MI

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Posted: 09/20/20 05:43am Link  |  Quote  |  Print  |  Notify Moderator

I think my 2 100AH LiFePo4 batteries are ok. I have not used them yet other than on 2 day trips due to my health. My alternator has a max capacity of 117 amps. It connects via #8 wire through 2 40 amp mini breakers to a battery isolator and then to the house batteries. I am attaching the specs for those batteries including the BMS protection, not sure if it will come. I hope you guys can confirm I am OK.

I do not know how to change this pdf file to a jpg I can attach. I could scan it into my pc then attach.
file:///C:/Users/Steve/Downloads/12V100Ah%20with%20BMS%20specs.pdf

It says max continuous charge current is 50 amps, and the max charge current is 60 amps or less.

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