Battery review: MRP 4S 850 mAh 45-90 C

MRP (Multirotorparts) has it’s own battery line-up. All 4S, all purely dedicated to mini quad racers in the world. The 850 mAh version is the tiniest pack of the family. This review will have a closer look at the  MRP 4S 1800 mAh 45-90 C battery.

How to use charts: This battery review contains some charts which can be interactively utilized. You are able to: Highlight any value just by clicking on the corresponding key below the chart. Hover over any value / line inside the chart to get precise readings. Right axis is always current. Have fun! :)

Appearance

The MRP lipo packs don’t feature any special design. The pack is protected by some black shrink wrapping. The sides are made of some textured white material, holding the single cells together. The front side has a colored product sticker glued to it, stating name and type of the battery. On the back you find a yellow sticker with the usual warning messages. Over all build quality is solid. No need to complain. Everything looks very well made and feels firm.

Technical Design

The MRP 4S 850 mAh 45-90 C pack is a standard 4S1P config flight pack for high power use.

Build Quality: Very good. Pack feels very well made on the outside. Connection terminal looks solid. Shrink wrapping job is good.

Plugs: The MRP batteries come with pre-installed XT60 connectors*. Plug and play for most of the pilots. The connectors sit very firm, good quality XT60s.

Cables: MRP uses 14 AWG wires on this packs. The high flexible silicon layer is rated up to 200°C. Cable length is about 9 centimeters.

Balacing plugs: Standard XT-system*. Balance wires are rather short (3 cm) which is a benefit in terms of getting them out of the way on your quad. The balancer plug is equipped with some transparent housing for easier unplugging. Balancer and main power leads are placed on top and bottom of the pack.

Technical Details

Manufacturer	MRP	(Click to enlarge.)
Type	MRP 45-90 C
Cell chemistry	Lithium Polymere (LiPo)
Cell type	LiPo
Cell count	4
Pack configuration	4S1P
Capacity	850 mAh
Max. Charge Current	4.25 A
Max. Discharge Current Continuous Burst	38.25 A 76.5 A
Weight w/o plugs with plugs	– ca. 101 grams
Measurements as listed measured	108 x 34,5 x 26.5 mm 108 x 33,5 x 26 mm
Price	16.50 €
Note	This battery has been directly donated by the manufacturer / distributor for review purposes.

Break-in documentation

The battery followed the standard break-in-process: The pack is charged at a rate of 1C until CV-phase ends with current of 1/10C. The break-in phase consists of four charging cycles at 1C and four corresponding discharges at 1 C / 4C / 10C and 20 C.

Anomalies: No anomalies during break-in.

Internal resistance measurements during break-in phase via iCharger 406B at 40°C pack temperature

Cycle	Cell 1	Cell 2	Cell 3	Cell 4	Total
After first charge	3.9	4.1	4.6	4.2	16.8
After second charge	3.6	3.7	4.1	4.0	15.4
After third charge	4.7	4.7	3.5	4.4	17.3
After fourth charge	3.8	4.5	4.2	4.0	16.5

Charging process

CV-Phase is really short on this cell type. Balancing in normal mode took 1:30 min. Cell drift during charge was unobtrusive. This is for 1C charge (0,85 A).

Load Testing

The main part of this battery test will consists of different load test settings showing the battery performance. Constant load testing is used to judge the advertised C-ratings as well as look at cell drift under high loads. We also check on internal resistance once more. Next up is the dynamic current test, which simulates a „real“ flight with changing (=dynamic) loads. For test methodology please check the dedicated methodology page!

Constant Load Testing

Constant load testing follows a certain load pattern of different constant currents. Base load is 10 C. Current pulses at 50 C, 35 C, 20 C and 30 C are maintained for time intervals between 10 and 20 seconds. For more details please refer to the test methodology page.

Capacity Usage

During this test the pack delivered 577 mAh. This is 67.8 % of nominal capacity. A good value.

Average cell voltages

The following table lists the average voltages per cell, of the total pack, as well as the averaged value per cell as fraction of total voltage during phase of active load.

	Cell 1	Cell 2	Cell 3	Cell 4	Total	Average per cell
Avg. Voltages	3.707	3.747	3.747	3.742	14.943	3.736

Just looking at average values the MRP 850 mAh pack performs well. All cells stayed above 3.70 V on average. An average value above 3.70 V / cell can be considered very good in this class.

Focus Voltages

Exceptionally interesting when testing a battery under a constant load for a longer period of time: the lowest voltage per cell just before load impulse is disabled. On top, you should have look at voltage recovery rate, that is: how fast do cell voltages rise again once load impulse is cut.

Phase	Cell 1	Cell 2	Cell 3	Cell 4	Total
End of 50 C	3.335	3.445	3.472	3.482	13.734
End of 35 C	3.421	3.504	3.513	3.526	13,963
End of 20 C	3.421	3.504	3.513	3.526	13.854
End of 30 C	–	–	–	–	–

The average cell voltage stability on the MRP pack can be considered good. Voltage only dropped below 3.5 V during 50 C discharge, which is outside of packs rated capabilities and therefore should not account negatively.

Average voltage recovery per second

Those values are specific to the test setting and not valid for the pack in general! Still they allow an estimated guess about how fast voltages rise again after current spikes.

	Cell 1	Cell 2	Cell 3	Cell 4	Total
Avg. Recovery [V/s]	0.0607	0.0478	0.0442	0.0402	0.193

Excessive voltage sag isn’t a problem for this battery. Recovery rates after current pulses are decent, too.

IR-Measurement

IR measurement is conducted using the four current pulses. Resistance for each cell is calculated in all four discharge phases. Shown values are averaged to cancel out different temperature points due to different discharge states during measurements.

Cell	1	2	3	4	Total
Resistance [mΩ]	6.49	5.39	4.95	4.04	15.64

Interpretation: The internal resistance of 5.22 mΩ average per cell indicates a „true“ C-rating of around 37 C (31 A). A very good valued and really close to the claimed 45 C rating. This calculation is on the conservative side and represents a current draw that will make the pack last for a long time. The pack had no problems delivering during high C discharge pulses. Voltage stayed above 3.5 V on this test for 35 C and 20 C loads. Handling 50 C for more than a few seconds will bring the pack to its limit, voltage sags heavily. As mentioned above this is outside of the pack’s specs, so that’s okay. It has to be noted that cell #1 is a little out of the total IR matching. This certainly becomes visible in the 25 C testing below.

Cell drift under load

Discharge Phase	50 C	35 C	20 C	30 C
Max Cell drift (V)	0.113 V	0.105	0.272	–

The MRP 850 mAh prototype has a acceptable cell drift during main discharge phase. To the very end of the cycle cells drift strong.

Key Temperature Facts

Temperature Development

All temperature probes reported values below cut-off point at 58°C. Max. temp during discharge was around 54.9 °C on the top of pack. Note that heating of stressed LiPo packs will continue for some more time even when load is cut.
Market Comparison

The following chart shows all reviewed LiPos in the same product segment for direct comparison of performance. Higher values under load are better.

Constant 25 C Discharge

Pretty much a standard benchmark in the LiPo industry.

Cut-Off /warning value for this battery should be chosen at 3.5 V minimum. After this point voltage drops very quick. The battery provided 567 mAh (66.7 %) during the 25 C discharge. You can see clearly how cell #1 is clearly the weakest, drifting away from the group already in the beginning.

Market Overview

Comparison of different reviewed >=1000 mAh batteries under 25 C load.

Dynamic Load Testing

The dynamic load testing setting consists of two separate discharge scenarios that have been developed of two different real-life FPV flights. Pattern one represents a high speed low proximity flight around the open field with some hovering to the end. Average load is around 22 A. Second pattern is a free-style flight around trees in the park with some current spikes near 70 A. Average load on this flight is around 13 A due to longer floating periods.

Capacity Usage

During the test of pattern 1 the pack delivered 501 mAh. This is 58.9 % of nominal capacity. In patter 2 testing 285 mAh (33.5 %) could be used until first cell reached cut-off voltage. This simply shows that this pack is not made for being used in big, current hungry 280 quads. But that’s nothing bad.

Market Compariso

The following charts give an overview of all tested packs in the >=1000 mAh class so far.

The last chart of this review sums up the usable capacity during all four load scenarios. Please note that this is only the capacity consumed by the electronic load! There are losses due to heating of the pack, which could be approximated (see testing methodology page). All four tests are cut when any cell goes below cut-off voltage of 3,3 V (or pack goes above 58 °C on any of the three probes). If you would push further and go down to 3,0 V/cell you will be able to squeeze out some mAh more, but at the cost of excessive heat generation and shortening of pack life-span. This value will most likely differ from what you get when flying on a quad as most people don’t monitor voltage on a per cell basis and therefore don’t even notice if voltage drops below 3,3 V/cell during punsh-outs (what’s not necessarily a good thing, though). For comparison, used capacity until 3,3 V/cell is reached is the base line in all battery reviews on Drone-Zone.de.

 

Conclusion

The MRP 4S 850 mAh 45-90 C battery is a tiny pack with an average capacity to weight ratio of 8.42 mAh/g. The 850 mAh class is dedicated to really small quads, e.g. 110 to 150 mm frame size. The fact that the smallest battery does not have the 65 C badge like the other smaller members of the MRP line up, makes it especially likeable. The pack performs great overall. Internal resistance lets us estimate a „true C rating“ of 37 C – that’s pretty close to the advertised 45 C! It has to be pointed out that two of the four tests run on the pack have been developed on larger 250 to 280 size quads with corresponding high current draws. Nevertheless, the little MRP pack handled loads above the 45 C rating noticeably well. Of course, the relative amount of capacity drained from the pack is small compared to larger packs – that’s due to the fact that this little friend had to go through some challenged way above it’s size. Constant current discharges show solid average voltages as well. Even if current drawn from this battery in some situations was higher than the rated specs, the pack stayed surprisingly cool. Only that one cell was clearly weaker than the other three can be listed on the contra side. Coming in at a price of 16.50 € the MRP 4S 850 mAh 45-90 C is a very honest battery and a great choice for micro sized high power quads. You also could throw this pack onto a small, thus demanding high speed wing.

Other packs of this line up reviewed:

• MRP 4S 1000 mAh 65-130 C
• MRP 4S 1300 mAh 65-130 C
• MRP 4S 1500 mAh 65-130 C
• MRP 4S 1800 mAh 65-130 C