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01-15-2025, 12:50 PM
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#1
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Senior Member
Winnebago Owners Club
Join Date: Feb 2008
Location: Spokane, WA
Posts: 167
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LifePo4 BMS charge current limit question
I'm looking into what hardware that I'll need to convert to LifePo4 batteries. I'd like to know if the batteries with a Bluetooth connected BMS have an option to set the max charge current? I'm hoping to eliminate the DC - DC charger to protect the alternator. It's a 130 Amp alternator.
I'm looking at either Wattcycle or LiTime.
__________________
Al and Deedee
2008 Winnebago Sightseer 29R F53, JMcKinley CHF, 5 Star tune, 2006 Honda CR-V, Blue Ox Aventa towbar
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01-15-2025, 12:55 PM
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#2
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Senior Member
Join Date: Apr 2022
Posts: 869
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Quote:
Originally Posted by atodalen
I'm looking into what hardware that I'll need to convert to LifePo4 batteries. I'd like to know if the batteries with a Bluetooth connected BMS have an option to set the max charge current? I'm hoping to eliminate the DC - DC charger to protect the alternator. It's a 130 Amp alternator.
I'm looking at either Wattcycle or LiTime.
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The BMS will likely have and fixed and not adjustable as it is more of a protective device than a control device. It is designed to protect the battery from damage. If you want to protect the alternator, fuse the circuit accordingly. If you have a large bank, you may blow the fuse, but that will be the point you want to invest in a DC-DC charger, imo. Start easy.
__________________
2021 Ram 3500 HO DRW Megacab 4wd 3.73
2022 Riverstone 42FSKG | GenY Executive 6.5k
Airlift 7500XL Airbags w Wireless One Compressor
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01-15-2025, 01:54 PM
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#3
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Senior Member
Join Date: Mar 2024
Location: Bohemia NY
Posts: 1,976
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Quote:
Originally Posted by atodalen
I'm looking into what hardware that I'll need to convert to LifePo4 batteries. I'd like to know if the batteries with a Bluetooth connected BMS have an option to set the max charge current? I'm hoping to eliminate the DC - DC charger to protect the alternator. It's a 130 Amp alternator.
I'm looking at either Wattcycle or LiTime.
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The trick to limiting battery charging current is to limit the size of the battery bank. What do you have now? What do you want? And what other connected loads do you have and support while driving? I would think that you now have 2 golf cart batteries or 2 RV/Marine for somewhere around 200-230 A/H. To go with Lithium as a "drop in" that likely should be limit. A 230 A/H Lithium direct connect will peak about 70 amps, taper to ~50-60 until approaching 90% state of charge. This is currently my go to for this type application.
https://www.amazon.com/Litime-Blueto...1zcF9hdGY&th=1
This battery with LTCP and Bluetooth is on sale. The BMS is extremely capable and actually turns off charging when battery is full.
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Dennis
Bohemia NY
2008 Nimbus 342 SE Carlyle
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01-15-2025, 01:59 PM
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#4
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Senior Member
Join Date: Jul 2014
Posts: 37,088
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DC to DC chargers do more then limit the current, they boost the charging voltage to lithium specs.
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01-15-2025, 02:14 PM
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#5
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Senior Member
Join Date: Mar 2024
Location: Bohemia NY
Posts: 1,976
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Quote:
Originally Posted by twinboat
DC to DC chargers do more then limit the current, they boost the charging voltage to lithium specs.
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Which is not needed or even desired on a daily basis. Anything over 13.6 to 13.8 volts will put charge current into them and ultimate voltage is 14.4 to 14.6 max. 14.0 to 14.2 will get them charged, just take a little bit longer.
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Dennis
Bohemia NY
2008 Nimbus 342 SE Carlyle
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01-15-2025, 02:51 PM
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#6
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Senior Member
Join Date: Jul 2014
Posts: 37,088
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Quote:
Originally Posted by d23haynes57
Which is not needed or even desired on a daily basis. Anything over 13.6 to 13.8 volts will put charge current into them and ultimate voltage is 14.4 to 14.6 max. 14.0 to 14.2 will get them charged, just take a little bit longer.
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Your opinion is based on what type of camping ?
Where are you getting 14.0 to 14.2 ? I have never seen that coming out of my alternator.
What is a little bit longer ?
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01-15-2025, 02:58 PM
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#7
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Senior Member
Winnebago Owners Club
Join Date: Feb 2008
Location: Spokane, WA
Posts: 167
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Quote:
Originally Posted by d23haynes57
The trick to limiting battery charging current is to limit the size of the battery bank. What do you have now? What do you want? And what other connected loads do you have and support while driving? I would think that you now have 2 golf cart batteries or 2 RV/Marine for somewhere around 200-230 A/H. To go with Lithium as a "drop in" that likely should be limit. A 230 A/H Lithium direct connect will peak about 70 amps, taper to ~50-60 until approaching 90% state of charge. This is currently my go to for this type application.
https://www.amazon.com/Litime-Blueto...1zcF9hdGY&th=1
This battery with LTCP and Bluetooth is on sale. The BMS is extremely capable and actually turns off charging when battery is full.
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Thanks, Dennis! Currently have (2) 6V GC2 batteries and will go with (2) 100 A/H LifePo4 as anything larger wont fit. We typically don't have any thing other than charging as a draw when on the road.
In regards to what twinboat mentioned in regards to the higher charging voltage of the DC - DC charger, we seldom travel more than a couple of hours prior to boondocking so I wont be relying on the alternator to get the last bit of voltage in them. I have an older PD4645 converter with the charge wizard and from what I hear, people at PD claim that I can hit the boost mode (14.4 V) the night before travel to top them off.
My main concern is alternator damage.
__________________
Al and Deedee
2008 Winnebago Sightseer 29R F53, JMcKinley CHF, 5 Star tune, 2006 Honda CR-V, Blue Ox Aventa towbar
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01-15-2025, 03:23 PM
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#8
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Senior Member
Join Date: Dec 2009
Location: North Texas
Posts: 1,111
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atodalen,
Seems to me that if you always leave with batteries topped off, you will never damage the alternator. If the battery bank is full - or close to it - they won't be demanding much from the alternator.
I assume by your statements that you have a generator and are able to charge the house batteries before hitting the road. . . . or at a minimum can charge from your generator as you drive. This would also presumably keep the load off your alternator.
On the other hand, if you think you're going to wake up from a night boondocking, fire up the main engine and drive (no generator) you do risk overloading you alternator. A DC-to-DC charger is going to be the way to go.
A lot depends on which boon docking model you follow.
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01-15-2025, 04:29 PM
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#9
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Senior Member
Winnebago Owners Club
Join Date: Feb 2008
Location: Spokane, WA
Posts: 167
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Quote:
Originally Posted by vtwinwilly
atodalen,
Seems to me that if you always leave with batteries topped off, you will never damage the alternator. If the battery bank is full - or close to it - they won't be demanding much from the alternator.
I assume by your statements that you have a generator and are able to charge the house batteries before hitting the road. . . . or at a minimum can charge from your generator as you drive. This would also presumably keep the load off your alternator.
On the other hand, if you think you're going to wake up from a night boondocking, fire up the main engine and drive (no generator) you do risk overloading you alternator. A DC-to-DC charger is going to be the way to go.
A lot depends on which boon docking model you follow.
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We do have a generator but there may be times that we don't have the opportunity to top off the batteries prior to leaving, thus the concern. I'm not averse to running the generator underway if I could be assured that it would be enough to lessen the alternator load enough.
Perhaps removing the house batteries from alternator charging will be a viable solution for my needs.
__________________
Al and Deedee
2008 Winnebago Sightseer 29R F53, JMcKinley CHF, 5 Star tune, 2006 Honda CR-V, Blue Ox Aventa towbar
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01-15-2025, 05:01 PM
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#10
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Senior Member
Join Date: Aug 2023
Location: sea level
Posts: 293
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From Todd at Progressive Dynamics:
How to reconfigure an old PD4645 to 14.4V for LiFePO4 batteries
This link will take you to pictures showing where the jumper can be installed IF the unit has the H6 connector that has the labels ‘LI’ and ’WIZ’ you would move the jumper so the center ping and the pin closet to ‘LI’ which will put it into lithium mode. The last picture in the link shows an older unit where the jumper on the H6 connector where the jumper would be connected.
When the jumper is moved the unit will put out 14.4 volts as long as there is a 120 vac to the converter.
The BMS of the lithium batteries will shut down when the battery is sufficiently charged.
https://www.progressivedyn.com/wp-co...r-settings.pdf
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01-15-2025, 05:02 PM
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#11
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Senior Member
Join Date: Dec 2009
Location: North Texas
Posts: 1,111
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Looking at the chart below, it appears the batteries you're looking at can draw as much as 100amps x 2 = 200. You're alternator's not going to like that.
Depending on the size of your charger. Do you happen to know what your PD4645 is capable of?
Or. . . . as you said, just disconnect the house batteries so they don't draw from the alternator. If that's an option.
Otherwise I'd say DC-to-DC may be you're only choice. Well . . . there's always a Li-BIM
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01-15-2025, 05:03 PM
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#12
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Senior Member
Join Date: Apr 2024
Location: WI Driftlesser
Posts: 2,547
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The Li will never be 0V or 6V or even 10V, so you can easily limit the current with out a DC-DC converter, if you don't need the voltage boost.
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"Bringing third world electrical work to first world luxury." RV makers of Murica!
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01-15-2025, 05:22 PM
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#13
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Senior Member
Join Date: Aug 2023
Location: sea level
Posts: 293
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I just got the new LiTime 12V 140Ah smart Bluetooth battery with 150A BMS.
The max charging current is 140A at 14..4V +/- 0.2V
Recommended charging current is 30A.
I will be installing it (single battery) with a Victron Orion -Tr smart 12 12 30 DC DC charger that is programmable , either standard LifePo4 setting or a user specified V out. My understanding is that it will prevent the alternator from burning up, since the battery’s internal BMS would otherwise allow it to draw up to 140A. The non-isolated version is a simpler 3 wire hookup.
From the LiTime website:
Smart Power Management with Bluetooth 5.0
Easily monitor and control your battery in real-time with Smart Bluetooth 5.0. Enjoy seamless auto-connection and smart features, including SOC, voltage, current, power, life cycles, and temperature monitoring. Control discharge on/off and switch the battery system remotely, giving you smarter, hassle-free energy management.
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01-16-2025, 08:33 AM
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#14
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Senior Member
Join Date: Nov 2018
Location: Beaver Dam, Wisconsin
Posts: 5,896
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A 130 amp alternator is exactly the size that tends to over heat while charging A pair of 100 amp hour lithium batteries.
The alternator needs to charge the chassis battery and run the engine 12 volt systems. There is not much left to charge a lithium battery at 60% state of charge or less. The alternator will be the most vulnerable when the engine is idling and the vehicle is stopped. That limits air flow for cooling.
There are several types of devices other than a B2B charger that can connect a lithium house battery and limit charging from the alternator.
Of course you can just disconnect alternator charging of the house battery.
There have been discussions about LiTime batteries in motor coaches. At least some of the LiTime batteries are not capable of running heavy duty slide motors or leveling systems.
The warranty specifically excludes failure replacement if one of these systems are installed in the RV. One owner was specifically refused warranty when the support desk asked if he had such a system in the RV.
__________________
Paul Bristol
Kodiak Cub 176RD
Nissan Pathfinder 2015
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