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| DC-DC Chargers, how to be kind to your alternator and house batteries [message #364461] |
Thu, 03 June 2021 07:18  |
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RF_Burns
Messages: 2276
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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So we all know the 80/90 Amp alternator on the GMC is heavily taxed when the house batteries are low. We all have stuff more battery capacity for the house systems than the original coach came with. If the house battery is low and the chassis battery just started the engine, the alternator is taxed to the maximum current it can deliver.
We also may have different battery types for the house and the chassis, each requiring a different charge voltage/current (wet, Gel AGM, LiFePO4).
Enter the DC-DC Charger. This unit takes the chassis alternator voltage and converts it to the proper voltage/current curve for the type of house battery you have. It also effectively replaces the Isolator so you no longer need that. The output of the alternator is connected directly to the chassis battery.
Batteries should be charged with a limited maximum current, especially when low and charge is initiated. Unfortunately, an alternator is a fixed voltage with its maximum current limited only by its internal resistance and operating RPM. With a pair of golf cart batteries at low charge and all the other vehicle current draws, upon initial startup the alternator could be delivering well beyond its rated capacity... not good. The DC-DC Charger limits this initial current to the house batteries and sets the maximum charging current to a safe level. This reduces the load on the alternator to a safe level.
They come in various current levels and some have an adjustment to the charger current. For my LiFePO4 battery conversion I chose a 20 Amp model from Renogy. After receiving the unit I found the Low Current (LC) mode reduces the charge current to 1/2 its rated current. When I was initially looking at these, the LC mode reduced the current to 12.5%, so that is why I choose the 20 amp model. With the LC now at 50%, I would go with the 40 Amp model. So the maximum charge current to the house battery from the alternator would be 40 Amps. I could reduce this to 20 Amps by switching the LC mode ON.
The DC-DC Charger charges the batteries with the same multi-stage charging curve as your "Smart" charger in your house converter, so your batteries are charged in a proper way for maximum life.
https://nerdtechy.com/best-12v-dc-battery-charger
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| [GMCnet] Re: DC-DC Chargers, how to be kind to your alternator and house batteries [message #364463 is a reply to message #364461] |
Thu, 03 June 2021 08:16  |
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I use this BIM in place of a DC DC charger. So far, after about a year, it
works as advertised.
bdub
On Thu, Jun 3, 2021 at 7:18 AM Bruce Hislop wrote:
> So we all know the 80/90 Amp alternator on the GMC is heavily taxed when
> the house batteries are low. We all have stuff more battery capacity for the
> house systems than the original coach came with. If the house battery is
> low and the chassis battery just started the engine, the alternator is taxed
> to the maximum current it can deliver.
>
> We also may have different battery types for the house and the chassis,
> each requiring a different charge voltage/current (wet, Gel AGM, LiFePO4).
>
> Enter the DC-DC Charger. This unit takes the chassis alternator voltage
> and converts it to the proper voltage/current curve for the type of house
> battery you have. It also effectively replaces the Isolator so you no
> longer need that. The output of the alternator is connected directly to the
> chassis battery.
>
> Batteries should be charged with a limited maximum current, especially
> when low and charge is initiated. Unfortunately, an alternator is a fixed
> voltage with its maximum current limited only by its internal resistance
> and operating RPM. With a pair of golf cart batteries at low charge and all
> the other vehicle current draws, upon initial startup the alternator could
> be delivering well beyond its rated capacity... not good. The DC-DC Charger
> limits this initial current to the house batteries and sets the maximum
> charging current to a safe level. This reduces the load on the alternator
> to a
> safe level.
>
> They come in various current levels and some have an adjustment to the
> charger current. For my LiFePO4 battery conversion I chose a 20 Amp model
> from
> Renogy. After receiving the unit I found the Low Current (LC) mode reduces
> the charge current to 1/2 its rated current. When I was initially looking
> at these, the LC mode reduced the current to 12.5%, so that is why I
> choose the 20 amp model. With the LC now at 50%, I would go with the 40 Amp
> model. So the maximum charge current to the house battery from the
> alternator would be 40 Amps. I could reduce this to 20 Amps by switching
> the LC
> mode ON.
>
> The DC-DC Charger charges the batteries with the same multi-stage charging
> curve as your "Smart" charger in your house converter, so your batteries
> are charged in a proper way for maximum life.
>
> https://nerdtechy.com/best-12v-dc-battery-charger
>
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| [GMCnet] Re: DC-DC Chargers, how to be kind to your alternator and house batteries [message #364464 is a reply to message #364463] |
Thu, 03 June 2021 08:17 |
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oops, forgot the link.
https://battlebornbatteries.com/product/lifepo4-battery-isolation-manager/
On Thu, Jun 3, 2021 at 8:16 AM Billy Massey wrote:
> I use this BIM in place of a DC DC charger. So far, after about a year,
> it works as advertised.
>
> On Thu, Jun 3, 2021 at 7:18 AM Bruce Hislop wrote:
>
>> So we all know the 80/90 Amp alternator on the GMC is heavily taxed when
>> the house batteries are low. We all have stuff more battery capacity for the
>> house systems than the original coach came with. If the house battery is
>> low and the chassis battery just started the engine, the alternator is taxed
>> to the maximum current it can deliver.
>>
>> We also may have different battery types for the house and the chassis,
>> each requiring a different charge voltage/current (wet, Gel AGM, LiFePO4).
>>
>> Enter the DC-DC Charger. This unit takes the chassis alternator voltage
>> and converts it to the proper voltage/current curve for the type of house
>> battery you have. It also effectively replaces the Isolator so you no
>> longer need that. The output of the alternator is connected directly to the
>> chassis battery.
>>
>> Batteries should be charged with a limited maximum current, especially
>> when low and charge is initiated. Unfortunately, an alternator is a fixed
>> voltage with its maximum current limited only by its internal resistance
>> and operating RPM. With a pair of golf cart batteries at low charge and all
>> the other vehicle current draws, upon initial startup the alternator
>> could be delivering well beyond its rated capacity... not good. The DC-DC
>> Charger
>> limits this initial current to the house batteries and sets the maximum
>> charging current to a safe level. This reduces the load on the alternator
>> to a
>> safe level.
>>
>> They come in various current levels and some have an adjustment to the
>> charger current. For my LiFePO4 battery conversion I chose a 20 Amp model
>> from
>> Renogy. After receiving the unit I found the Low Current (LC) mode
>> reduces the charge current to 1/2 its rated current. When I was initially
>> looking
>> at these, the LC mode reduced the current to 12.5%, so that is why I
>> choose the 20 amp model. With the LC now at 50%, I would go with the 40 Amp
>> model. So the maximum charge current to the house battery from the
>> alternator would be 40 Amps. I could reduce this to 20 Amps by switching
>> the LC
>> mode ON.
>>
>> The DC-DC Charger charges the batteries with the same multi-stage
>> charging curve as your "Smart" charger in your house converter, so your
>> batteries
>> are charged in a proper way for maximum life.
>>
>> https://nerdtechy.com/best-12v-dc-battery-charger
>>
>
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bdub
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| Re: DC-DC Chargers, how to be kind to your alternator and house batteries [message #364469 is a reply to message #364461] |
Thu, 03 June 2021 11:04 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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interesting as I am aware of problems trying to charge super dead batteries with the alternators. I have seen quite a few "rescue" coaches burn up alternators on the 1st trip, and I always attribute that to the fact that the house battery bank is pretty much shot and the alternator is working overtime.
I have my battery monitor, and when my house bank is low I make a point to utilize the generator and the PD9560 converter to do the work because I feel it has ability to get the charge up in the housebank the quickest.
I might have to look into these.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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