|
|
Post by vasko on Oct 8, 2015 19:34:31 GMT
I've measured today the amps consumption of the starter motor of my 2.5TD Citroen XM - 130bhp - the starter is rated at 2.2kw - e.g. the theoretical maximum should be around 2200/12 = 183amp. Car was cold and haven't been started for about a week. The results are - 1/2 sec 168 amps and after that to 60-70 amps. Initially I did not disarmed the alarm to make sure that the engine will not start and I can record properly the consumption , second time I disarmed the alarm to enable the engine to start - result are the same. After this and putting in the equation that my boat starter motor is actually rated 1.1kw e.g. maximum theoretical consumption - 1100/12 = 91 amps - way lower than the one on the car I decided to get for my starter battery a drop-in replacement for lead-acid - LiFePo4 - 20AH - arranged the shipping to my boat and will give it a try in two weeks  this way I will be able to use the space of my current started battery for another house battery The LiFePo4 battery that I choosed can supply 20AH and max current 200amps - which means about 10+ minutes proper turning of the starter which should be well enough including in worst case scenario and the cycles of the LiFePo4 and no self discharge and can be charged from lead-acid battery charge - e.g. drop in replacement. Price also looks quote good! www.ev-power.eu/LiFeYPO4-batteries-12V-1-1/Lithium-Battery-LiFePO4-12V-20Ah.htmlvideo of the test for reference if some want to do the same and gain space: ( will upload video starting the boat and consumption of LiFePo4 too ) |
|
|
|
Post by Damir on Oct 9, 2015 4:51:01 GMT
Hi Vasko In the winter currents will be higher because the oil is cold and thick. If you think to reduce the dimensions of the battery think well because the engine is notn ew and there is always something can happen. Have on board the cable with clips for reconnect the battery . You do not get much in the area but it's your ship, and you decide. |
|
|
|
Post by rxc on Oct 9, 2015 17:36:53 GMT
Remember that the rating of the motor is a steady-state value, and starting currents for motors can be 3-5 times higher than rated, full load currents. Don't know how you measured the current - transients like that can be tricky to measure.
|
|
|
|
Post by vasko on Oct 9, 2015 17:51:30 GMT
anyway - I already ordered the LiFePo4 battery and will give it a try and will write here my finding - on paper the things look very good - will know how they look in practice after some time another video here from another source comparing batteries: |
|
|
|
Post by vasko on Oct 9, 2015 17:59:29 GMT
another one from battery producer:
|
|
|
|
Post by Damir on Oct 9, 2015 19:14:48 GMT
I wish you lots of luck with the new battery and is eagerly waiting for the written finding. |
|
|
|
Post by so36idavid on Oct 9, 2015 21:26:38 GMT
Do I understand you to mean that you're going to charge it in parallel with your house bank, with no additional charge control electronics? My impression is that the charge profile for Li-ion batteries looks quite different from a traditional lead acid battery. Have you looked into this or are you just going for it and seeing what happens?
David
|
|
|
|
Post by vasko on Oct 10, 2015 8:44:40 GMT
Yes, without additional charge controller - the LiFePo4 batteries can be used as "drop-in" replacement if you do not want to get the battery fully charged and have real longer life from it - e.g. I decided on 20ah battery instead of 10ah as I will expect the battery to be charged no more then 50-60% winch is well enough for 4 minutes of turning the starter - which is a very long time - a engine should start in about 5 sec turning in normal circumstances.
in brief if yo do not need a full changed LiFePo4 battery then drop-in replacement is OK.
parameters of the battery that I have decided on :
------------
Nominal voltage of the battery is 12 V and the operational voltage is 11,5 V - 14,8 V.
The maximum charging voltage for initial charge is 15 V.
Recommended subsequent charging is to 14,8 V.
The minimum voltage is 11 V.
Maximum discharge current is 3C continously.
Operating temperature -20°C up to 65°C (discharging)
|
|
|
|
Post by vasko on Oct 10, 2015 8:47:30 GMT
|
|
|
|
Post by vasko on Oct 10, 2015 9:00:30 GMT
you can read this one too : gwl-power.tumblr.com/post/363583077/faq-using-lifepo4-batteries-as-starting-batteries---------------------------------- FAQ: Using LiFePO4 batteries as starting batteries for the fuel cars (2) Q: How will the LiFePO4 battery be affected by the charging system of the car? A: The 12V LiFePO4 battery is not affected by the charging system at all. Majority of the cars’ charging systems charge up to 14V or 14.4V. This represents the charging level of 70% to 75% for the LFP batteries. Q: Will the car charging system overcharge the LFP battery and shorten its life? A: No. The overcharge for LFP battery is above 17V. There is no way to reach this voltage in the vehicle. As the LFP battery has no memory effect, it can be charged any time to any capacity. There is no shortening of the life-span when using as a starting battery. Q: What is the starting time for the fuel engine when using 12V LiFePO4 battery? A: The starting time for any fuel engine is given by the vehicle manufacturer. Usually it is about 5 to 10 seconds. This time is the same for LFP battery. In any case, the fuel engine should not be started with long starting attempts. Please see the vehicle instruction for starting the engine. Q: What is the max current available from the 12V LFP battery? A: The 12V LiFePO4 battery can release the energy very quickly without any limitation. The peak short connection current may reach above 1000A. Unlike lead-acid batteries that are limited by the Peukert’s law (http://en.wikipedia.org/wiki/Peukert’s_law), the LFP batteries do not have any such limitation. However due to the high energy release, the LFP batteries should not be extremely discharged for longer than 10 seconds. The discharge table for 12V 40Ah LP LiFePO4 battery 20 A current - min. 120 minute use (2 hours) 40 A current - min. 60 minute use (1 hour) 60 A current - min. 40 minute use 200 A - max 10 s. peaks - approx 70 times (70*10s = 700 s. ~ 12 minutes) 400 A - max 10 s. peaks - approx 35 times (35*10s = 350 s. ~ 6 minutes) 1000 A - max 5 s. peaks - approx 18 times (18*5s = 90 s ~ 1.5 minute) |
|
|
|
Post by so36idavid on Oct 10, 2015 23:28:47 GMT
Way cool, please report back after you've been using it for a while.
David
|
|
|
|
Post by vasko on Oct 26, 2015 21:11:43 GMT
I can now confirm after a week sailing in cold weather that the LiFePo4 20AH drop-in replacment battery is the best battery I have ever tested !
-delivers easily 1000+ CCA capable of VERY happy turning my starter for more the 10 min
-starts engine in seconds in 5 degree C
- able to recharge in second
- if discharged can be charged with 40ah e.g 1/2h from 0 to nearly 100%
compared to my 8 months old Varta LFD75 is about 15 times cheaper (taking the cycles in account) and about 1000x better by feeling
in brief I'm not going to buy a Lead Acud battery for my cars or boat ever again
|
|
this way I will be able to use the space of my current started battery for another house battery 
