question

neepsandtatties avatar image
neepsandtatties asked

Outboard alternator charging lithium

Question

To charge a 12V LiFePO4 from an outboard alternator charging coil, what product is suitable to regulate the charging?

System Components

Outboard: Manual start, Honda BF6, 12V 6A charging coil
Battery: Lithium (LiFePO4), 12Ah, max charging rate 0.8C (9.6A)

Research Done

Watched the Victron Q&A Webinar 1 - Using an Alternator to charge Lithium video, and understand that since the battery has a larger C rating than the alternator, alternator current must be restricted using a Smart Orion or similar.

Victron Options Found

Using the VictronConnect app to check the interfaces via the demo mode. Nothing appears suitable:

- Phoenix Smart Charger IP43 12|30 has "maximum charge current" settings of 7.5A, 15A and 30A, the minimum is too high for the alternator.

- Orion Smart 12V|14V-18A Isolated has a LiFePO4 battery preset but no current limit settings (just voltage), and it isn't clear if it's ok with the variable output from an outboard.

- Blue Smart Charger 12|5 can limit charging to 2A or 7A, but is mains powered, and the 2A lower limit loses 4A of potential charging, while the 7A upper limit is too high for the alternator.

- SmartSolar Charger 100|15 can limit charging on a variable scale in 1A increments, but it's inputs are designed for panels only (MPPT controller won't turn on until incoming voltage exceeds Vbat + 5V. Thereafter the minimum PV voltage is Vbat + 1V), it's also unclear what the MPPT varying the exposed load will do to the outboard coil.

Non-Victron Options Found

- Sky RC B6 Charger + Sterling Alternator Protection Device this combination is promising. The B6 charger can tolerate a range of input from 11-18V, and 6A maximum output. SkyRC were unclear under what circumstances the battery would be disconnected, and so there is a danger of damaging the alternator by having the battery disconnected during engine running.

This danger can be minimised using a Sterling device that provides an emergency route for current in the case of disconnection or failure. Sterling device is waterproof.

The battery pack accepted in the spec of the B6V2 is 100-50000mAh (unclear what happens if the battery is over-spec). Also Victron members mention it being difficult to configure. It is not waterproof and so extra weather protection must be added.


Which Victron product will allow the charge to be limited to a safe current for the alternator?

screenshot-2021-12-02-at-193907.png


I am in a 3m open-top inflatable boat so the system needs to be compact, light, and simple.

Update May 2022: added promising (unfortunately non-Victron) option

With the existence of the alternator protector, any charging product that can accept variable and lumpy voltage inputs of ~5V-18V while limiting output to 6A and disconnecting if overloaded seems like the perfect solution.

battery chargingLithium Batterychargerorion-tr smartalternator
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8 Answers
ddickov avatar image
ddickov answered ·

Hi there I think you maybe require the Orion dc to dc charger range I hope this helps. Sorry just seen you had checked that one, I would try a victron agent who might be able to advise accordingly thanks david

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kevgermany avatar image
kevgermany answered ·

Looks like your alternator isn't up to it. Sorry.

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neepsandtatties avatar image neepsandtatties commented ·
This question is relevant for any deployment where the battery charging current is smaller than the battery Ah -> most of them!
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mbischa avatar image
mbischa answered ·

Most small outboards don't have an alternator and only a 6a output that requires a regulator(normally nothing more than a bridge rectifier, no charge regulation), I am not sure what else it requires.

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kevgermany avatar image
kevgermany answered ·

For clarity.

Lithium requires different charging than lead based batteries.

Most, if not all, alternators are set up for lead based batteries.

Charging lithium with an alternator through a non-restrictive charger may result in the alternator running at high power for long periods, possibly causing overheating and damage.

Orions will only restrict charge rate if their capacity is smaller than the alternator output.(gross oversimplification)


If it is is necessary to charge lithium batteries from a low output alternator and there isn't a suitable orion, consider a charger for hobby use, such as the iMax B6 and its clones. They are not waterproof, setup is painful, need to be started manually, shutoff is automatic. But once configured, it is simple to use. It is also inexpensive.

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neepsandtatties avatar image neepsandtatties commented ·
Thank you, I will contact SkyRC about their iMax line and report back. I understand whatever product the does the current limiting must not disconnect the outboard alternator while the engine is running or it will damage the coil.
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kevgermany avatar image kevgermany ♦♦ neepsandtatties commented ·

I can't see how it can disconnect the coil. But once the charge cycle is finished, current drops close to zero. I guess if you're worried about how fast this happens, you could add a small lead battery across the alternator output..

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sergeysorokin avatar image
sergeysorokin answered ·

It seems like Smart BMS CL 12/100 may be a solution you are looking for. Looks like CL stands for Current Limit, and from what is written in manual, it looks like it can be configured to lowest charging current among all Victron products (Orion DC-DC will start from 200+ W).
I have not checked if it really works, only reading docs now...

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neepsandtatties avatar image neepsandtatties commented ·

If you look at the demo interface for the BMS CL in the Victron Connect app, the product does not have an adjustable current limit, just a 'Battery charge limit' in Volts.

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sergeysorokin avatar image sergeysorokin neepsandtatties commented ·
Yes, is not configurable via App, because the manual says that current is adjusted by selecting appropriate fuse, which is used as shunt. However crazy this may sound, have a look at table 1 in manual for CL12/100... But, the problem for you may be that minimal current listed in manual is 9A for 2x7.5A fuses.

For me 9A seems like a usable limit, so I'm going to give it a try, but most likely this will be next summer.
If you can find someone with CL12/100, you can ask them to try if using lower rating fuse will produce lower current, which it should, unless there is some sort of protection/whatever inside, which will prevent operation in such mode.
Otherwise, just find any other (non Victron) DC-DC charger with low current and use Cyrix-Li-Charge to disconnect charger on BMS alarm.

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Sarah avatar image
Sarah answered ·

Hi, I am curious as to what sort of load you have on the battery and why you have chosen lithium (size/weight?). It may be cheaper to go out and buy a small VRLA battery.

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neepsandtatties avatar image neepsandtatties commented ·

Primary reason for lithium in this setup is energy to weight/size ratio - I have to portage whole kit in a pack on foot, and it's easily the lightest and least bulky way to carry around that amount of power (aside from gasoline, which is why I want to be able to tap that energy source in the simplest way possible).

The loads are light. LA batteries are not :)

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jared-armstrong avatar image
jared-armstrong answered ·

I have the same issue and so far have had no luck in finding a solution. I'm currently stuck to just charging via solar but sounds like that may not be viable for you.

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kevgermany avatar image
kevgermany answered ·

For something like this, I would get a small charger like the imax b6. These are programmable for battery type, charge current etc., take a wide range of dc input. But read the manual, it is confusing with lithium. The flow chart in the manual is the best method.

Downside is they're not waterproof and also need to be switched on manually.

You can rig up a light waterproof housing. Might work with plastic food boxes with clip on lids, but they seem to be prone to splitting where you drill for wires. There are also aluminum ones which might work better. Obviously seal the wires an protect them from chafing where they go through the housing.

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